The technique for directly implanting artificial hairs in human skin has been remarkably developed in recent years, and various types of artificial hairs and their implanting appliances have accordingly been improved in a number of forms. As to the shapes of the root portions of the hairs, for instance, various proposals have been made including providing an ampoule shape (U.S. Pat. No. 4,024,315), an arrowhead shape (Japanese Patent Publication No. 54-11744), a looped shape and a knot which is formed at the root portion.
As to hair implanting appliances, on the other hand, various developments have been made including a hollow needle (U.S. Pat. No. 4,004,592), an air gun type hair implanter (Japanese Patent Publication No. 54-11744), a hair implanting needle formed with a recess at its tip (U.S. Pat. No. 4,004,592), a pincette-shaped hair implanting needle (U.S. Pat. No. 4,004,592) and a bifurcated needle (U.S. Pat. No. 4,004,592).
The most slender hair implanting needle according to the prior art has an outside limit diameter of 0.3 mm for the case of a hollow structure and a limit diameter of 0.35 to 0.5 mm for the case of a bifurcated or similar structure. This is because it becomes difficult to insert any artificial hair into the hollow needle which has a smaller outside diameter than the above-specified value. In the case of a bifurcated needle, having a smaller diameter than the above-specified value, it may bend when the needle is pierced into the skin, so that it cannot carry out its function. If, moreover, the thickness of the needle is excessively reduced, the retaining operation of the artificial hair at the tip of the bifurcated needle becomes so deficient as to cause the hair implanting operations to be deteriorated.
In order to enhance the fixation percentage of the artificial hairs implanted, emphasis has been placed upon the shape of the hair root portion for increasing its resistance to extraction and upon research for the developments of needles which are best suited for implanting the artificial hairs.